How does Voyager 4220 UC negotiate connections and playback focus with multiple devices?

[Anonymous]

 I would like to know what are the mechanisms/decisions that the multipoint Voyager 4200 uses to:

1. Arbitrate between which paired devices will make a connection, when multiple paired devices (from the 8 possible) are in range
   and
2. Decide which audio (from the 2 possible connected devices) will be given the focus, and play on the headset, at any point in time.

The Voyager 4200 user guide says: "...your headset can connect to mobile and PC. Your headset remembers up to 8 devices, but connects to up to 2 devices at a time".

I have three devices paired to my headset and in range in my office:
1. My PC (with a BT600 USB dongle, and which sometimes I plug the Voyager 4200 in directly via USB)
2. My iPhone (connecting through Bluetooth)
3. A Chromecast with Google TV (which, despite the name, is an Google Android device, which connects as a Bluetooth phone, including a headset profile)

The PC with the BT600 seems to always connect/take precedence (if it's turned on), but the iPhone and Chromecast seem to compete with each other. Sometimes the iPhone will connect as "phone 1"; sometimes the Chromecast will connect as "phone 1". Alternatively, if the PC is off, one will connect as "phone 1" and the other will connect as "phone 2".

Once the headset had made these initial connections, are these choices locked in -- or can I manipulate the connections from the phone, like having the headset disconnect "phone 2", so the PC can connect, or having the headset drop "phone 1", if the iPhone, so the Chromecast can connect as "phone 1" instead? Or, are these connections outside of my control and I just need to manually go to the connected BlueTooth device and have it initiate the disconnect to free up a connection on the headset?

Similarly, if two devices are connected, what prompts the Voyager 4200 to switch sound from one device to another? It seems like if I am listening to a A2DP from my PC on the headset, and I do anything on my phone (e.g. something trivial that would trigger a UI audible feedback), the headset will automatically switch to playing the phone audio and interrupt the audio stream from the PC. For example, if I am watching a training video on my PC (e.g. from the Pluralsight website), and I open my phone and either play a YouTube video, or even just open Twitter (even if Twitter sound is muted), the streaming sound from the PC will mute and the phone sound (even if muted) will take over in the headset. This seems undesirable. Of course, I can understand a second device interrupting audio playing from the first device in an "alert" situation (like an incoming call), but not for just any trivial audio/UI event on the second device. What determines this audio focus shift between connected devices, and can it be better controlled by the user? I would rather have to manually switch to phone audio only when desired, rather than have it automatically just take over at times when a shift of focus would be disruptive.

Thanks for any insights into how device connections and audio focus work with this multipoint headset. It seems unpredictable with no rhyme or reason so far, and it makes using the headset a frustration.